This invention relates to a mobile telephone device, such as an automobile telephone device, having an aging operation function.
A mobile telephone device of the type described comprises a serial interface for connecting the mobile telephone device to an external device such as a handset. The serial interface comprises a clock terminal for supplying a clock signal to the external device and a serial data terminal for receiving serial data from the external device. The mobile telephone device comprises an antenna plug. In a normal state for a normal operation, the antenna plug is connected to an antenna.
In order to detect early or initial failure of the mobile telephone device before shipment of the mobile telephone device, the mobile telephone device has an aging operation function. When the mobile telephone device carries out an aging operation, the mobile telephone device is put into an aging state. In the aging state, the mobile telephone device is continuously or intermittently put into a transmission state.
According to prior art, a mobile telephone device comprises a particular terminal which is called an aging terminal. The aging terminal is exclusively used when the mobile telephone device is subjected to the aging operation. More specifically, the aging terminal is supplied with a logic low level when the aging terminal is grounded. Otherwise, the aging terminal is supplied with a logic high level. If the aging terminal is grounded, the mobile telephone device carries out the aging operation after power is applied to the mobile telephone device. In other words, the mobile telephone device judges whether the mobile telephone device is subjected to the normal operation or the aging operation in accordance with a logic level supplied to the aging terminal when the power is applied. When the mobile telephone device is subjected to the aging operation, the antenna plug is connected to a terminating set for restraining radiation of undesirable radio wave.
Attention will be directed to the normal state where the antenna connected to the antenna plug. It will be assumed that a user erroneously grounds the aging terminal. In this event, the conventional mobile telephone device carries out the aging operation when the power is applied to the conventional mobile telephone device. Accordingly, the conventional mobile telephone device radiates the undesirable radio wave which interferes with a mobile telephone system. In addition, it is necessary to provide the conventional mobile telephone device with the particular terminal on subjecting the conventional mobile telephone device to the aging operation. Therefore, the conventional mobile telephone device is disadvantageous in that it has a large-size and is expensive.